Abstract:

The resistance of seven jujube strains (species),5 of these,Zizyphus jujuba var. Dunzizao,Zizyphus jujuba var. Changhongzao,Zizyphus jujuba var.Mayazao,Zizyphus jujuba var. Hupingzao and Zizyphus jujuba var. Hamazao,selected from Chinese genebank of jujube in Shanxi Fruit Tree Research Institute,other two of these:Zizyphus jujuba var.Pozao and Zizyphus Spinosa selected from Tang County,Hebei province,to jujube witches-broom disease was determined by using the method of grafting diseased bark onto the seedlings from 1995～1999.The results are as follow:The percent of seedlings infected by the disease for Z.jujuba var.Dunzizao is 100%,Z.jujuba var. Mayazao is 78.57%, Z.jujuba var.Changhongzao is 66.67%, Z.jujuba var.Pozao is 100%, Zizyphus Spinosa is 80%,Z.jujuba Hamazao is 0% and Z.jujuba var. Hupingzao is 0%.This indicates that Z.jujuba var. Hupingzao and Z.jujuba var. Hamazao have high resistance to the jujube witches-broom disease.112 seedlings belonging to 45 individuals of Pozao jujube selected from the epidemic area of the disase in Taihang Mountain,Hebei province,were planted in experiment site in Tang County in 1995.From 1996～1997,by using the grafting method the phytoplasmas caused the disease were infected artificially twice.In the third time,the phytoplasmas were artificially infected by grafting some infected twigs onto the seedlings of jujube selected in April 1998.The results investigated in October 1999 showed that 6 seedlings belonging three individuals have not been infected by the disease.Though 3 of these belonging to 2 individuals grew some little diseased twigs in May and June 1998 just after grafting diseased twigs on them, these diseased twigs all died in next spring,and the seedling have grown well.

Key words: Jujube tree, Jujube witches-broom disease, Phytoplasmas, Resistance, Selection